Research On Shunt Active Power Filter Based On Adaptive Algorithm

Along with lots of power electronic equipments being put into use, the harmonic pollution of power system is growing up, which increases power quality problems. Because of the increased demand of power quality, the traditional harmonic inhibition and reactive power compensation method used LC passive filter can't meet the requirements. In virtue of many high-power power electronic devices being developing, active filtering technology has made great headway, and its advantages are increasingly evident. Active power filter is a new type power electronic equipment which is able to compensate the harmonics whose frequency and amplitude are changing. Active power filter can overcome some shortcomings of passive filter device, so it's paid wide attention.Regarding shunt active power filter as the research object, this paper focuses on two important aspects which include harmonic current detection and compensated current tracking control. The detection link uses a harmonic current detection algorithm based on adaptive noise canceling technology. With the analysis of LMS algorithm, a novel variable step-size adaptive algorithm of harmonic current detection which uses the average estimation of the error signal to control the updating of step-size and weight values has been put forward. After using variable step-size algorithm, the system doesn't need eclectic selection between steady-state accuracy and convergence rate and can be controlled flexibly. This algorithm uses the average estimation of the error signal to control the updating so that it can reduce the noise impact of the gradient estimate effectively and improve on the system steady-state accuracy. On that basis, it adds momentum in the iterative process of weights to speed up the convergence process. In the compensation current tracking control, the system adopts hysteresis control method of timing comparison, which can make the output current of main circuit track the directive current and limit the maximum switching frequency of the main circuit switching device. At the same time, DC-Side voltage control link is added in the control system to maintain the stability of the DC-Side voltage.Based on the research in the above, the studies in this paper also have some guidance on the design of structure and parameters. And the detailed simulation on MATLAB has been done. The simulation results verify the effectiveness of this system in harmonic inhibition and reactive power compensation.In the end, the total work is summarized, and some insufficiencies are pointed out. Then the follow-up work is forecasted.